The fake news story was posted on the satire site "Abril Uno" on January 21st. From the article:

Phillip Morris, the world’s biggest cigarette producer, announced today that they will join the marijuana legalization bandwagon and start producing marijuana cigarettes. Marketed under the brand “Marlboro M”, the cigarettes will be made available for sale through marijuana-licensed outlets in the state of Colorado, and the state of Washington when it becomes commercially legal there later this year...

Since only tobacco products are currently banned in advertisements and promotions in the United States, Phillip Morris also has set aside a huge $15 billion advertising budget just to promote the new “Marlboro M” and are now negotiating with major networks and publishers, to start marketing the product to consumers in the beginning of 2015...

Phillip Morris shares hit an all-time high on the marijuana news and shot up to $998.00 from $83.03 just a few hours after the announcement went public.

It seems like more and more fake news sites are popping up every day. For instance, Abril Uno (which is Spanish for April 1st, i.e. April Fool's Day) only came into existence on January 14, according to the whois data. And less than two weeks later, they've already got a viral story.

On the subject of marijuana cigarettes, the Legends & Rumors site notes that back in the 1960s and early 70s a rumor circulated alleging that the big tobacco companies were eagerly anticipating the day when pot would be legal, and that many of them had already registered names for their planned marijuana cigarettes. In March 1971 tobacco-company executives sent letters to Rolling Stone magazine denying these rumors.